Revealing the interrelation between C- and A-exciton dynamics in monolayer WS2 via transient absorption spectroscopy

Two-dimensional transition metal dichalcogenides (TMDs) are emerging as a promising complement for traditional semiconductor materials in ultrathin optoelectronic device fields. Developing a better understanding of high-energy C-exciton dynamics is essential for efficiently extracting hot carriers and building high-performance TMD-based light-harnessing devices; however, insight into the C-exciton dynamics remains scarce. To further understand the C-exciton dynamics, here, we have unraveled the interrelation between C-exciton and band edge A-exciton dynamics in monolayer WS2 by transient absorption spectroscopy. It is found that the band edge A-excitons could effectively generate high-energy C-excitons via the many-body process, and, in turn, the hot carriers relaxing from C-excitons to band edge states could compensate and slow the decay of the A-excitons. The comprehensive understanding of the interrelation between C-exciton and A-exciton dynamics in monolayer TMDs may trigger the potential applications for future TMD-based light-harvesting devices.